Device for adjusting series of golf clubs and series of golf clubs thus adjusted

ABSTRACT

The invention relates to a method for adjusting a series of golf clubs each comprising a shaft, a head at the proximal end of the shaft and a grip at the distal end of the shaft; said method comprising the following steps: adjusting the mass of the head of each golf club and/or, adjusting the mass of the shaft near the distal end of the shaft, such that each golf club has a substantially identical moment of inertia; then adjusting the mass of the grip of each golf club and/or adjusting the mass of the shaft near the proximal end of the shaft, such that each golf club has a substantially identical swingweight. The invention also relates to a series of golf clubs adjusted using the method according to the invention.

FIELD OF THE INVENTION

The present invention relates to the field of golf. More specifically, the invention relates to a method for adjusting a series of golf clubs as well as a series of golf clubs adjusted using this method.

BACKGROUND OF THE INVENTION

Playing golf requires the use of several golf clubs, also called clubs. Each club comprises a shaft, a head at one end of the shaft to strike the golf ball, and a grip, at the other end of the shaft, by which the golf player holds the club. Among golf clubs, there are three main families based on the head of the club: woods, irons and the putter. Each player generally has several irons and several woods making it possible for the golf ball to fly over different distances. Typically, a golf player will have between 6 and 11 irons and between 2 and 5 woods.

The movement performed in order to propel the ball with the golf club demands great precision from the player. To be able to repeat this movement irrespective of the club used by the player, it is desirable to adjust the golf clubs such that the player finds the same sensations regardless of which club is used.

To date, different methods are used to adjust golf clubs. The most widely used method consists of adjusting a player's golf clubs with a constant swingweight. The swingweight is a well-known golf parameter characterizing the static equilibrium of the golf club. It is measured using a swingweight scale (such as the Professional Digital Swingweight Scale marketed by AUDITOR under reference 020711 or the Clubmaker Classic Swingweight Scale marketed by AUDITOR under reference 020320). It can also be calculated using the equation described in detail in the mathematical formula [Math 1] of the examples below. Some players may prefer to have more weight at the head or, on the contrary, in the grip. The swingweight characterizes this static distribution of the mass. By choosing a constant swingweight for each golf club, the player will find similar sensations, from club to club, in the starting position when he raises the club before beginning to swing. The adjustment of golf clubs with a constant swingweight is favored by manufacturers, who, by default, supply clubs for which the weight of the head and the length of the shaft varies so as to obtain a constant swingweight between the different clubs.

It is also possible to adjust the golf clubs with a constant moment of inertia. The moment of inertia of the golf club characterizes the resistance to rotation of the golf club along an axis passing through the proximal end of the shaft (that is to say, the end of the shaft at the grip). The moment of inertia is measured using a moment of inertia scale (such as the MOI Speed Match System marketed by AUDITOR under reference 070206). It can also be calculated using the equation described in detail in the mathematical formula [Math 2] of the examples below. By choosing a constant moment of inertia for each golf club, the player will find similar sensations, from club to club, during the swing, in particular during the transition between the backswing and the downswing as well as during the release. For two golf clubs having the same swingweight and two different moments of inertia, the player will have the same sensation before swinging, but a different sensation during the movement, and in particular during the transition between the end of the backswing and the beginning of the downswing, as well as the crucial moment of release before striking the golf ball. Conversely, for two golf clubs having the same moment of inertia and two different swingweights, the player will have the same sensation during the movement, but a different sensation in the starting position before the swing when he weighs the clubs in his hands.

The adjustment of the moment of inertia is done by modifying the mass at the head of the golf club. This modification systematically causes a modification of the swingweight. At this time, no method is known making it possible to adjust a series of golf clubs with a constant moment of inertia and a constant swing. Such an adjustment would allow the golf player to obtain homogeneous sensations, from club to club, both in his starting position as well as during movement.

One of the aims of the present invention is therefore to propose a method for adjusting the golf clubs of a player with a constant moment of inertia and constant swingweight in order to promote the regularity of the player and allow him to have the same sensation regardless of the golf club used.

BRIEF DESCRIPTION OF THE INVENTION

The inventor has noted that the modification of the mass near the proximal end of the shaft causes a modification of the swingweight while modifying the moment of inertia very little or not at all. Indeed, the moment of inertia characterizes the resistance to rotation of the golf club along an axis passing through the proximal end of the shaft; the addition or removal of mass on, or near, the axis of rotation has no impact on the setting in rotation. The inventor uses this feature to allow the adjustment of the swingweight of a golf club without modifying the moment of inertia thereof.

Thus, the present invention relates to a method for adjusting a series of golf clubs each comprising a shaft, a head at the proximal end of the shaft and a grip at the distal end of the shaft; said method comprises the following steps:

-   -   adjusting the mass of the head of each golf club and/or         adjusting the mass of the shaft of each golf club near. the         distal end of the shaft, such that each golf club has a         substantially identical moment of inertia along an axis passing         through the proximal end of the shaft; then     -   adjusting the mass of the grip of each golf club and/or         adjusting the mass of the shaft of each golf club near the         proximal end of the shaft, such that each golf club has a         substantially identical swingweight.

As described in detail hereinabove, the adjustment of the mass of the shaft near the proximal end of the shaft and/or the adjustment of the mass of the grip is done without modifying the moment of inertia of the club. The adjustment of the mass of the head of each golf club and/or the adjustment of the mass of the shaft of each golf club near the distal end of the shaft is therefore done before adjusting the mass of the grip of each golf club and/or adjusting the mass of the shaft of each golf club near the proximal end of the shaft. At the end of the adjusting method according to the invention, a series of golf clubs is obtained in which each golf club has a substantially identical moment of inertia and a substantially identical swingweight. Of course, one of the golf clubs from the series of golf clubs serves as a reference; this golf club cannot be subject to adjustments. This is generally the golf club that is best suited to the player.

The adjustment of the moment of inertia is done by adjusting the mass of the head and/or adjusting the mass of the shaft near the distal end of the shaft. In one embodiment, in order to adjust the mass of the head of each golf club, at least one tip weight is added or removed in the head. Some golf heads typically have a cavity in which it is possible to insert or remove one or several tip weights thus allowing an adjustment of the mass of the head. These tip weights typically have a mass of several grams. According to one embodiment, the mass of a tip weight is 2, 3, 4, 5, 6, 7, 8, 9 or 10 g. In one embodiment, in order to adjust the mass of the head of each golf club more specifically, powder, preferably metal powder such as tungsten powder is added to or removed from the head, in particular the cavity of the head. In one embodiment, in order to adjust the mass of the shaft near the distal end of the shaft, at least one tip weight is added to or removed from the shaft, near the distal end of the shaft—this distal end of the shaft generally penetrates inside the head so as to allow the connection between the shaft and the head. According to one embodiment, the mass of such a tip weight is 2, 3, 4, 5, 6, 7, 8, 9 or 10 g.

The adjustment of the swingweight is done by adjusting the mass of the shaft near the proximal end of the shaft and/or by adjusting the mass of the grip. In order to modify the swingweight without altering the adjustment of the moment of inertia previously done, it is important to modify the mass of the club only near the proximal end of the shaft. The closer the modification of the mass is to this end, the less the moment of inertia will be modified. In one embodiment, in order to adjust the mass of the grip, the grip is replaced by a grip with a different mass. Preferably, the difference in mass is located near the proximal end of the grip, for example by using a different material. Alternatively, at least one tip weight is added to or removed from the grip, preferably near the proximal end of the grip. According to one embodiment, the mass of a tip weight is 2, 3, 4, 4, 5, 6, 7, 8, 9 or 10 g. In one embodiment, in order to adjust the mass of the shaft near the proximal end of the shaft, at least one tip weight is added to or removed from the shaft near the proximal end of the shaft. According to one embodiment, the mass of a tip weight is 2, 3, 4, 4, 5, 6, 7, 8, 9 or 10 g. According to one embodiment, in order to make it possible to add a tip weight in the shaft near the proximal end of the shaft, an intermediate sleeve is used. This intermediate sleeve is inserted by friction into the proximal end of the shaft and contains one or several tip weights.

It can also be advantageous for the golfer to adjust his golf clubs such that each golf club has a constant address position. Thus, in one embodiment, the method according to the invention also comprises adjusting the address position of each golf club by modifying the length of the shaft and/or the lie angle, such that each golf club has not only a substantially identical swingweight and moment of inertia, but also a substantially identical address position. This step for adjusting the address position of each golf club is carried out before adjusting the moment of inertia of each golf club. This step for adjusting the address position of each golf club can also be carried out after adjusting the swingweight of each golf club. It is possible to determine the address position of a golf club as a function of the lie angle and the length of the shaft by means of formula [Math 3] A=L×sin(Li) where A is the address position, L is the height relative to the ground and Li is the lie angle. These parameters are illustrated in [FIG. 5].

According to a second aspect, the invention also relates to a series of golf clubs adjusted using the method according to the invention. In one embodiment, the series of golf clubs is a series of irons. In one embodiment, the series of golf clubs is a series of woods.

Definitions

“Near the proximal end of the shaft” refers to a small distance from the proximal end of the shaft in light of the length of the shaft (for example at a distance from the proximal end of the shaft smaller than 20%, 10%, 5% or preferably 1% of the total length of the shaft) or at the proximal end of the shaft.

“Near the distal end of the shaft” refers to a small distance from the distal end of the shaft in light of the length of the shaft (for example at a distance from the distal end of the shaft smaller than 20%, 10%, 5% or preferably 1% of the total length of the shaft) or at the distal end of the shaft.

“Address position” refers to the height of the golf club when the head is in contact with the ground.

“Distal” refers to the part furthest from the player's hands when the player is holding the club.

“Lie angle” refers to the angle formed by the shaft with the sole of the head of the club.

“Proximal” refers to the part closest to the player's hands when the player is holding the club.

“Series of golf clubs” within the meaning of the present invention refers to at least two golf clubs belonging to the same family; in other words, at least two irons or at least two woods, preferably at least three irons or at least three woods, still more preferably at least four irons or at least four woods. According to one embodiment, a series of golf clubs can comprise at least two woods and at least two irons, at least three irons and at least three woods, or at least four irons and at least four woods.

“Substantially identical” means identical to within plus or minus 1%, preferably identical to within plus or minus 0.1%.

“Substantially identical moment of inertia” means a moment of inertia identical to within plus or minus 1%, preferably identical to within plus or minus 0.5%, even more preferably identical to within plus or minus 0.1%.

“Substantially identical swingweight” means a swingweight value (see FIG. 1) identical to within 1 point, preferably identical to within 0.5 point, even more preferably identical to within 0.1 point.

“Substantially identical address position” means an identical address position to within plus or minus 3 millimeter, preferably identical to within plus or minus 2 millimeter, even more preferably identical to within plus or minus 1 millimeter.

“Swingweight” refers to the static equilibrium of a golf club. This static equilibrium of the golf club can for example be measured by the Professional Digital Swingweight Scale marketed by AUDITOR under reference 020711 or the Clubmaker Classic Swingweight Scale marketed by AUDITOR under reference 020320.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the swingweight scale as a function of the swingweight value obtained using formula [Math 1] or a swingweight scale.

FIG. 2 schematically illustrates a golf club.

FIG. 3 schematically illustrates a golf head comprising a tip weight.

FIG. 4 schematically illustrates the proximal end of a grip and a shaft in which a tip weight is inserted.

FIG. 5 schematically illustrates the address position (A), the length (L) and the lie angle (Li) of a golf club.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 illustrates a golf club (1) comprising a shaft (2) connecting a head (3) to a grip (4). Each golf club from a series of golf clubs comprises these 3 elements.

As indicated above, in order to adjust a series of golf clubs such that each golf club has a substantially identical moment of inertia and a substantially identical swingweight, the masses are adjusted. Of course, one of the golf clubs serves as a reference. This club may not be subject to any adjustment or may be subject to an adjustment desired by the user.

First of all, the mass of the head of each golf club and/or the mass of the shaft of each golf club near the distal end of the shaft is adjusted, such that each golf club has a substantially identical moment of inertia. As illustrated in [FIG. 3], this adjustment can be done by adding a tip weight (5) into the head (3) of the golf club. Preferably, as illustrated, this tip weight is introduced at the end of the orifice serving to connect the shaft (2) and the head (3). According to one embodiment, the moment of inertia is typically set within a range of values from 1800 to 2800 kg·cm².

Once the moment of inertia is adjusted, the mass of the grip of each golf club and/or the mass of the shaft of each golf club near the proximal end of the shaft is adjusted, such that each golf club has a substantially identical swingweight. As illustrated in [FIG. 4], this adjustment can be done by adding a second tip weight (6) into the shaft (2) at the proximal end of the shaft under the grip (4). This adjustment of the swingweight is done with a constant moment of inertia. According to one embodiment, the swingweight is typically set within a range of swingweight values from −10 to 8, i.e. within a range of swingweight scale from C0 to D8.

At the end of the adjusting method, one therefore obtains a series of golf clubs all having a substantially identical moment of inertia and a substantially identical swingweight.

EXAMPLES

Calculation of the Swingweight

As an example, the swingweight can be calculated as follows (cf. Computing Heft, The Tutleman site, Oct. 8, 2018,

https://www.tutelman.com/golf/design/swingwt2.php):

$\begin{matrix} {{SW} = {\frac{{{Lc} \times \left( {T + \frac{S}{2}} \right)} - {14\mspace{11mu} \left( {T + S} \right)} - {10 \times G}}{50} - 124}} & \left\lbrack {{Math}\mspace{14mu} 1} \right\rbrack \end{matrix}$

where

-   -   SW is the swingweight rounded to the closest unit;     -   Lc is the length of the club (in inches);     -   T is the weight of the Head of the club (in grams);     -   S is the weight of the shaft (in grams);     -   G is the weight of the grip (in grams).

Calculation of the Moment of Inertia

As an example, the moment of inertia can be calculated as follows (cf.

Computing Heft, The Tutleman site, Oct. 8, 2018, https://www.tutelman.com/golf/design/swingwt2.php):

$\begin{matrix} {{M\; O\; I} = {{{Lc}^{2} \times \left( {T + \frac{S}{3}} \right)} + {10 \times G}}} & \left\lbrack {{Math}\mspace{14mu} 2} \right\rbrack \end{matrix}$

where

-   -   Lc is the length of the club (in inches);     -   T is the weight of the Head of the club (in grams);     -   S is the weight of the shaft (in grams);     -   G is the weight of the grip (in grams).

Calculation of the Influence of the Change in Weight of the Grip on the Swingweight and the Moment of Inertia.

Consider the example of a 5 iron with a length of 38 inches (Lc), whereof the weight of the head (T) is 254 grams, the weight of the shaft (S) is 90 grams and the weight of the grip (G) is 50 grams.

This iron has a swing value of 4 and a moment of inertia of 410,596 g·inch². According to the swingweight scale illustrated in [FIG. 1], this iron therefore has a swingweight of D4.

In the hypothesis of a change of grip, it is possible to calculate the influence of the use of a grip of 60 grams (or 10 grams more than the previous grip) on the swingweight and the moment of inertia of the iron.

With a grip of 60 grams, one obtains a swingweight of 2 and a moment of inertia of 410,696 g·inch². The swingweight of this iron is therefore henceforth D2 (cf. the swingweight scale in [FIG. 1]), which represents a very sensitive variation for a knowledgeable golf player, while the moment of inertia remains practically unchanged (variation of 2 per 10,000).

This shows that, in order to adjust the swingweight to a target value without changing the moment of inertia, it suffices to add weight to or remove it from the top of the shaft, near or on the grip, which is done easily by adding or removing tip plates in the top of the shaft or changing the grip. This method makes it possible to obtain a set of clubs all having a substantially identical swingweight and moment of inertia.

Adjustment of the Address Position

Let us consider the example of a series of 9 irons, one iron of which (for example a 6 iron or a 7 iron) serves as reference iron. Knowing the address position of the reference iron and knowing that the length difference between the successive irons of a series is known—in this example ⅜ inches—it is possible to adjust the lie angle by calculation from formula [Math 3] in order to obtain a series of golf clubs having a constant address position, i.e. a substantially identical address position. 

1. A method for adjusting a series of golf clubs each comprising a shaft, a head at a proximal end of the shaft and a grip at a distal end of the shaft; said method comprising the following steps: adjusting the mass of the head of each golf club and/or adjusting the mass of the shaft of each golf club near the distal end of the shaft, such that each golf club has a substantially identical moment of inertia along an axis passing through the proximal end of the shaft; and adjusting the mass of the grip of each golf club and/or adjusting the mass of the shaft of each golf club near the proximal end of the shaft, such that each golf club has a substantially identical swingweight.
 2. The adjusting method according to claim 1, further comprising adjusting the length of the shaft of each golf club and/or adjusting the lie angle of each golf club, such that each golf club has a substantially identical address position.
 3. The adjusting method according to claim 1, wherein the adjustment of the mass of the head of each golf club is done by adding or removing at least one tip weight in the head.
 4. The adjusting method according to claim 1, wherein the adjustment of the mass of the head of each golf club is done by adding or removing powder in the head.
 5. The adjusting method according to claim 1, wherein the adjustment of the mass of the shaft of each golf club near the distal end of the shaft is done by adding or removing at least one tip weight in the shaft near the distal end of the shaft.
 6. The adjusting method according to claim 1, wherein the adjustment of the mass of the grip of each golf club is done by replacing the grip with a grip having a different mass.
 7. The adjusting method according to claim 1, wherein the adjustment of the mass of the grip of each golf club is done by adding or removing at least one tip weight in the grip.
 8. The adjusting method according to claim 1, wherein the adjustment of the mass of the shaft of each golf club near the proximal end of the shaft is done by adding or removing at least tip weight in the shaft near the proximal end of the shaft.
 9. A series of golf clubs adjusted using the method according to claim
 1. 10. The series of golf clubs according to claim 9, wherein the head of each golf club comprises an iron or a wood.
 11. A series of golf clubs, each comprising a shaft, a head at a proximal end of the shaft and a grip at a distal end of the shaft; wherein said series is adjusted using the following steps: adjusting the mass of the head of each golf club and/or adjusting the mass of the shaft of each golf club near the distal end of the shaft, such that each golf club has a substantially identical moment of inertia along an axis passing through the proximal end of the shaft; and adjusting the mass of the grip of each golf club and/or adjusting the mass of the shaft of each golf club near the proximal end of the shaft, such that each golf club has a substantially identical swingweight. 